This invention relates generally to transducers, and, more particularly, to an elliptical, interdigital transducer which will create an acoustic wave in a piezoelectric medium.
A transducer is any device or element which converts an input signal into an output signal of a different form. An example would be a microphone which converts vibrations caused by an impinging sound wave into an electrical signal.
The most widely used class of transducers is the electromechanical transducer which converts an electrical signal into a mechanical signal (a vibration or a displacement) or vice versa. This class includes phonograph pickups, loudspeakers, horns, doorbells and underwater transducers.
In the simplest of surface wave transducers, a piezoelectric film is deposited on a substrate, and two metal contacts are deposited on the piezoelectric coating. When the metal contacts are excited with an A.C. voltage, the contacts are alternately "pulled together" and "pushed apart" by the electric field. This pushing and pulling in the piezoelectric medium is transmitted to the substrate, and travels along the surface of the substrate.
In an interdigital transducer, more contacts are added, physically and connected electrically in parallel. The increased number of "fingers" will, if properly spaced, increase the amplitude of the surface wave due to constructive interference.